THE ORIGIN OF RED BEDS 155 



States Geological Survey), and from laboratory study of thin 

 sections. For valuable suggestions and criticism and for review of 

 the manuscript the writer is indebted to Messrs. Eliot Blackwelder, 

 A. N. Winchell, W. J. Mead, and F. T. Thwaites, of the University 

 of Wisconsin; to Messrs. W. H. Emmons, C. R. Stauffer, F. F. 

 Grout, C. J. Posey, and A. W. Johnston, of the University of 

 Minnesota; and to Dr. R. D. Salisbury, of the University of 

 Chicago. 



SUMMARY DESCRIPTION OF THE FEATURES CONSIDERED 



List of formations. — -Clastic sedimentary strata of reddish color 

 outcrop or constitute the uppermost part of the bedrock over about 

 4 per cent of the area of the United States and exist beneath a 

 cover of younger sediments under an additional area probably twice 

 as large. Much the greatest volume of such strata is included in 

 the single group of rocks which forms the subject of the present 

 study: namely, those Red Beds which outcrop in many areas from 

 Kansas and Texas to Arizona and Montana (Fig. 1). The forma- 

 tions included in this group are related closely in age, ranging 

 from Pennsylvanian to Triassic, or possibly Jurassic, and are prob- 

 ably for the most part physically continuous. They comprise the 

 Cimarron series of Kansas and Oklahoma, and the Wichita, Clear 

 Fork, Double Mountain, Greer, Quartermaster, and Dockum beds 

 of Texas; the Wyoming, Fountain, and Maroon formations of 

 central Colorado ; the Cutler and Dolores of southwestern Colorado ; 

 the Aubrey, Shinarump, Vermilion Cliff, and Moencopie of the 

 Colorado Plateau, with the Saliferous and Zuni of the Zuni Plateau 

 in New Mexico; the Spearfish, Opeche, and Chugwater of Wyoming 

 and southern Montana; and the Ankareh and Nugget of south- 

 eastern Idaho and northeastern Utah. 



Similar Red Beds constitute a large part of the sediments of the 

 Newark series (Triassic) of the Appalachian Piedmont region- 

 typified by the Stockton and Brunswick formations of New Jersey. 1 

 They make up also, among others, much of the Catskill formation 

 (Devonian) of eastern New York and Pennsylvania; the Medina 

 and Clinton (Silurian) of New York; the Vernon shale (Silurian, a 



1 See H. B. Kiimmel, Ann. Rept. of the State Geologist of New Jersey, 1896. 



